Automatic control system for front end loader

ABSTRACT

Automatic control system for a front end loader utilizing a bucket or fork at the end of a rigid boom. An automatic digging and dumping cycle is in parallel operation with a manual control system and which automatic control system may be changed to manual by an operator or be preselected for automatic or manual operation. Pressure sensitive means are utilized to determine and control the position and attitudes of the various elements that perform the necessary work functions.

O United States Patent [151 3,643,828

Elliott 1451 Feb. 22, 1972 [54] AUTOMATIC CONTROL SYSTEM FOR 3,375,5964/1968 Bacquie ..2l4/778 x FRONT END LOADER 3,487,958 1/1970 Shook eta1. ..214/138 X [72] lnventor: James H. Elliott, 1441 Stoneygate Lane,primary Examiner A|ben Makay Columbus. Ohio 43221 AssistantExaminer-John Mannix 9 Attorney-Anthony Cennamo 21 Appl. No.: 840,367[57 ABSTRACT Automatic control system for a front end loader utilizing a[52] U.S.Cl ..214/762,214/41 bucket or fork at h n f a rigi m- Anautomati 51 1111. c1. ..E02t3/00 digging and dumping cyele is inParallel operation with a [58] Field ofSearch ..214/762,778,771,138,132, manual control System and which automatic control System214/41, 764 may be changed to manual by an operator or be preselectedfor automatic or manual operation. Pressure sensitive means 56]References Cited are utilized to determine and control the position andattitudes of the various elements that perform the necessary work func-UNlTED STATES PATENTS lions- 3,339,763 9/1967 Caywood et a1. ..214/138 4Claims, 6 Drawing Figures PATENTEDFEBZZ I972 3.643 .828

SHEET 1 OF 6 FIG. I

- INVENTOR. JAMES H. ELLIOTT I ww ATTORNEY AUTOMATIC CONTROL SYSTEM FORFRONT END LOADER BACKGROUND From end loaders generally consist of aleading bucket mounted on the front of a tractor chassis (of some typeor special manufacture) by two parallel arms. These arms are actuatedeither by mechanical means or by hydraulic cylinders. The machine isoperated by lowering the bucket to the desired level, driving themachine into the spoil pile (which in turn loads the bucket), backingthe machine out of the spoil pile, raising the bucket, driving theloader to the desired unloading point, and then dumping the bucket. Atthat time, the bucket is lowered and the loader driven back to the spoilpile. The loader units find their most valuable applications in loadingout bulk material from stockpiles, loading trucks in sand and gravelpits, backfilling excavations, loading shot material in mines, etc.

The front end loaders in present use require the constant attention ofthe operator to the various functions. The operator must operatenumerous levers and steering mechanisms to carry out the necessarysequence of operations. Throughout each step of the digging and loadingoperation, the operator must make continual decisions as to thenecessary attitudes and movements of the digging bucket, and pull orpush levers at the proper time to direct the digging cycle. For thesereasons, considerable time and attention is required of the operator tomaintain efficient operation and maximum loading rates.

SUMMARY OF INVENTION The automatic hydraulic control system of thisinvention is adaptable to operate in parallel with a manually operatedcontrol system so that the operator of the loader may choose eithermanually or automatically to operate the machine, may pick any portionof the cycle as manual or automatic, and may switch from manual toautomatic operation and vice versa at any stage of the operation. Manualoperation of the loader requires the operator to dexteriously positionthe lift arms, bucket and loader by manipulation of levers to controlthe arms and bucket and by levers, foot pedals and steering apparatus toposition the loader. The invention provides an automatic control systemin which the lift arms and the bucket are automatically actuated,relieving the operator of the effort andjudgement normally required andallowing the operator to concentrate on moving the loader itself.

OBJECTS The primary object of this invention is to provide a systemwhich will automatically cause some of the loading and dumping functionsto be performed, thereby allowing the operator to spend a greaterportion of his time in the driving and safe handling of the loader.

Another object of this invention is to provide an automatic loading anddumping cycle which may be placed in parallel with the manual controls.

Another object of this invention is to provide an automatic loading anddumping cycle, of which any desired portion can be preselected by theoperator for either manual or automatic operation.

Still a further object of this invention is to provide an automaticloading and dumping cycle which can be changed at the operator's will,at any portion of the cycle, from manual to automatic and vice versa.

Other objects and advantages, as well as a full understanding of theinvention, will be had from the following description and claims, takenin conjunction with the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a side 'elevational view ofa carrier and front end loader to which the automatic hydraulic controlsystem of this invention has been applied;

FIG. 2 is a pictorial flow diagram and electrical schematic of apreferred embodiment of the basic automatic control system;

FIG. 3 is a pictorial flow diagram and electrical schematic of theautomatic control system with certain of the control valves combined;

FIG. 4 is a pictorial flow diagram and electrical schematic of theautomatic control system of this invention and differs from FIG. 3 inthat a different transducer than the torque converter has been used todetermine the loading resistance to the bucket;

FIG. 5 is a pictorial flow diagram and electrical schematic of theautomatic control system of this invention and differs from FIG. 3 inthat a modulating valve is used to control the bucket movements duringthe loading process; and

FIG. 6 is a pictorial flow diagram and electrical schematic of theautomatic control system of this invention and differs from FIG. 3 inthat a modulating valve is used to control the bucket movements duringthe loading process, and a different transducer than the torqueconverter has been used to determine the loading resistance to thebucket.

DESCRIPTION OF THE PREFERRED EMBODIMENT In accordance with the generalconcepts of the invention and with reference to the drawings, a pressuresensitive means is utilized together with the lift arms, the lift arm tobucket connection, the lift arm to loader connection, etc., providing asignal output when the loading resistance to the loader increases abovea value preselected by the operator, Means responsive to the signaloutput is utilized to actuate the bucket cylinder and lift arm cylindersto decrease the loading attitude of the bucket and raise the lift arms.When the loading resistance decreases to less than the preselected valuethe responsive means is deactivated. The loader machine includes meansresponsive to the bucket load. In this way, when the operator reversesthe loader transmission, a limit switch is actuated (if the pressuretransducer in the lift arms senses a vertical load on the bucket) andsignals the bucket cylinder valve to tilt the bucket to carry position.Also actuated is the lift arm cylinder valve to raise the bucket to apreselected height. Limit switches are provided to stop the fluid flowto the bucket cylinders and lift cylinders whenever the bucket reachesthe carry position and carry height. The loader machine further includesmeans to automatically dump the bucket when the loader contacts the sideof the dumpv truck. A

limit switch, mounted on the loader engages the side of the truck body,another limit switch on the lift arms senses that the lift arms are atdump height, and a signal is sent to the bucket cylinder control valveto dump the bucket. This in turn provides hydraulic fluid under pressureto the bucket cylinders and pivots the bucket to the dump position. Asthe bucket reaches the dump position, a limit switch mounted on the liftarms is actuated and shuts off the bucket control valve, therebystopping fluid flow to the bucket cylinders and leaving the bucket inthe dump position. The loader machine also includes means toautomatically lower the bucket and return it to a loading attitude andheight when the carrier vehicle is backed away from the dump truck bythe operator. As the limit switch mentioned above disengages the side ofthe truck body, another limit switch senses that the bucket is in thedump position, another limit switch senses that the carrier vehicle isin reverse, a limit switch senses that the lift arms are in the raisedposition and a relay is engaged which actuates the control valve to thebucket cylinder. The hydraulic flilid flows from the source to thebucket rams, tilting them back until the bucket actuates a limit switchon the lift arms and stops the bucket in the preset load position. Atthe same time that the bucket starts its return to the load position,the relay actuates a delay timer in the circuit to the lift arm lowervalve. This timer is field adjustable by the operator to allowsufficient time for the bucket to finish clearing the side of the truck.At the end of the preset period, the lift cylinder lower valve isactuated and the bucket is automatically lowered until it reaches apreset height. At that time a limit switch measures the elevation of thelift arms and disengages the relay supplying power to the lift cylindervalves, shutting off the flow of fluid and stopping the bucket at thecorrect height for loading.

Referring now to FIG. I, a front end loader is shown consisting of thebasic components of a carrier vehicle 1, having mounted at the frontthereof a pair of lift arms, indicated generally by the number 2, abucket 3 pivoted to the end of the lift arms 2, a doubleor single-actingpair of rams 4 pivotally connected at one end to the carrier 1 and atthe other end to the lift arm 2 whereby the lift arm 2 is pivoted in avertical plane, these rams being known as the lift cylinders or rams.One or two double-acting rams are pivotally connected at one end to thelift arm assembly 2 and at the other end to the bucket assembly 3 whereby the bucket 3 is pivoted in a vertical plane, these rams being knownas the bucket cylinders or rams.

All of the components of the front end loader machine described to thispoint are standard in the industry. The bucket 3 is controlled byhydraulic fluid pressure directed into the rams 4 and S, the fluid flowbeing normally directed by an operator manipulating manual valve 8,generally indicated. In addition, the carrier 1 has a steering wheel 6,plus various other controls such as throttle, brake, gear shift, clutch,etc., all of which are common to wheeled or tracked carriers. Typically,there are two levers operating the manual valve 8, each of whichbasically consists of a closed center three-position valve, wherein thevalve pushed outwardly conducts fluid to cause a ram to operate in onedirection and, when pulled inwardly, conducts fluid flow to cause a ramto move in the opposite direction with the center position being the offor noflow position.

The present invention consists essentially in its most general sense ofapplying, to the typical hydraulically operated from end loader unitdescribed to this point, an electric-hydraulic control system wherebysubstantially all of the manual manipulation of the valves 8 is replacedby automatically controlled systems.

Referring now to FIG. 2, a pictorial flow diagram is shown of the basichydraulic circuit of a preferred embodiment wherein the loading,raising, carrying, dumping, and repositioning for loading cycles areautomatically controlled.

With specific reference to FIG. 2, and continued reference to the loaderof FIG. 1, of the automatic loading cycle, there is positioned inparallel with the manual valves 8A and 8B, a solenoid operatedtwo-position automatic load valve 7. This valve 7 controls hydraulicfluid pressure to the lift side of the lift ram 4 and the curl side ofthe bucket ram 5 when the solenoid 7a is energized, and blocks themovement of the rams when the solenoid 7a is deenergized. The operationof the hydraulic circuit is initiated when the lift arms 2 are loweredto the loading position closing limit switch 26 mounted on thecarrier 1. The bucket 3 is then leveled to the loading attitude closinglimit switch 27 mounted on the lift arm 2 assembly, as the mode selectorswitch 9 and the master automatic switch 10 are energized, thetransmission of the carrier is in low gear closing limit switch 28. Whenthe operator drives the loader bucket into the spoil pile and the bucketof the loader encounters sufficient resistance, the pressure in thetorque converter 14 will rise and transmit a signal to the pressureswitch 61. The pressure at which the contacts of switch 61 close isadjustable by the operator depending upon the type of soil being loadedand the condition of the ground the loader is operating on. At a presetpressure of the torque converter, somewhere just below the stall pointof the carrier, the contacts of switch 61 will close and energize thesolenoid 7a of the automatic loading valve 7. Fluid will flow viahydraulic line 38 from the carrier source 30 to the flow divider 15 andthen to the lift side of the lift ram 4 and the curl side of the bucketram 5. The flow divider 15 will insure that the bucket 3 will curl in apredetermined ratio to the amount of lift of the bucket. This isaccomplished as the flow divider will split the flow from valve 7 in apredetermined ratio between the bucket cylinder 5 and the lift cylinder4. As the bucket is raised, the amount of bucket curl will be in directproportion to the amount oflift. As the bucket 3 lifts and curls in thespoil pile, the resistance to the loader bucket 3 will decrease and theloader bucket 3 will drive deeper into the spoil pile. At the same time,the lessened resistance to the loader bucket 3 will decrease thepressure in the torque converter 14, open the contacts of pressureswitch 61 and stop the movement of the bucket 3 until sufficient bucketresistance is again encountered to start the cycle all over again. Inthis manner the loader continually moves into the spoil pile under theconstant drive of the automatic transmission and the bucket raises andcurls to obtain a full load. Pressure switch 61 will be preset by theoperator to a value that raises and curls the bucket 3 just before theloader stalls or starts to spin its wheels, whichever occurs first. Assoon as the bucket 3 is full, the operator reverses the carrier vehicle7, this opens limit switch 28 and deenergizes the automatic loadingsolenoid valve 7. At any time the automatic loading cycle can be stoppedby either opening the master control switch 10, the mode selector switchauto load 9, or by operating either of the manual control valves 8A and8B which in turn will open their respective limit switches 37 and 39.Any of the above operations will deenergize the automatic loadingsolenoid valve 7. However, as soon as the manual control valves arereturned to the neutral position, their limit switches will close andrestart the loading cycle at a point where it was stopped.

For the automatic raising cycle, positioned in parallel with the manualvalves 8A and 813, respectively, are solenoid operated two-positionvalves, lift arm automatic raise valve 16 and bucket automatic carryvalve 17. The lift arm automatic raise valve 16 controls hydraulic fluidpressure to the lift side of ram 4 when the solenoid 16a is energized,and blocks the movement of the rams 4 when the solenoid 16a isdeenergized. The bucket automatic carry valve 17 controls the hydraulicfluid pressure to the curl side of the bucket rams 5 when the solenoid17a is energized and blocks the movement of the bucket 3 when thesolenoid 17a is deenergized. The operation of the automatic raise cycleis initiated when the operator energizes master automatic switch 10,mode selector switch auto raise 11, loads the bucket and shifts thecarrier transmission to reverse.

When limit switch 31 is closed by the reverse lever of the transmission,pressure switch 35 measures the hydraulic fluid pressure in the bucketlift rams 4 and determines that the bucket 3 is loaded. When thepressure switch contact 35 closes, it completes a circuit to theauxiliary relay 29, the contacts on the relay 29 close and hold therelay 29 energized regardless of whether or not the transmission is nowplaced in reverse or forward. At the same time that the auxiliary relay29 is energized, a circuit is completed to both solenoids 16a and 17a ofthe lift arm automatic raise valve 16 and bucket automatic carry valve17. Hydraulic fluid under pressure is sup plied via hydraulic line 44 atfull volume through valve 17 to the bucket curl ram 5 and tilts thebucket 3 to the carry position. When the bucket 3 is in the properposition for carry, limit switch 53, mounted on the lift arm assembly 2,is actuated by the bucket 3 and opens the circuit to the solenoid 17a ofvalve 17. This in turn blocks the bucket ram 5 in the carry position. Atthe same time that the automatic bucket carry valve 17 is energized, theautomatic lift arm raise valve 16 is energized. In this conditionhydraulic fluid under pressure is supplied via hydraulic line 40 throughthe adjustable flow restrictor 18 to the lift arm cylinders 4, raisingthe bucket 3 in the air. The purpose of the flow restrictor controlvalve 18 is to give the bucket time to tilt from the load position tothe carry position before it gets too high in the air. Also on roughterrain, an operator would adjust the rate of lift of the bucket so thatit would not be high in the air for any period longer than necessary andwould reach its maximum height just as the carrier was approaching thetruck. When the bucket 3 reaches the proper height in the air, a presetlimit switch 33 mounted on the carrier 1 would contact the lift arm 2,limit switch contact 33 would open deenergizing both the auxiliary relay29 and the automatic lift arm raise valve 16 which in turn would shutoff the fluid flow from the lift arm rams 4 and hold the bucket 3 in theraised position.

As in the automatic loading cycle, the automatic raise cycle can bestopped at any time either by opening the master control switch 10, themode selector switch auto raise 11, or by operating either of the manualcontrol valves 8A and 8B which in turn will open their respective limitswitches 37 and 39. Any of the preceding operations will deenergize theauxiliary relay 29, the automatic raise valve 16, and the automaticcarry valve 17. However, as soon as the manual control valves arereturned to the neutral position, their limit switches will close andrestart the raise and carry cycle where it stopped, provided that thetransmission is still in reverse. Check valves 19, 20, and 25 preventthe hydraulic fluid from flowing in the wrong direction and actuating aram at the wrong time.

For the automatic dump cycle, positioned in parallel with the manualvalve 8B, is a solenoid operated two-position automatic dump valve 21.This valve controls hydraulic fluid pressure to the dump side of thebucket ram 5 when the solenoid is energized, and blocks the movement ofthe ram when the solenoid 21a is deenergized. The operation of thehydraulic cycle is initiated when the master automatic switch 10 and themode selector switch automatic dump 12 are energized. The lift arms areraised to the dump position closing limit switch 59 mounted on thecarrier 1. The bucket 3 is in the carry position closing limit switch 55mounted on the lift arm assembly, and the operator drives the carrier upto the truck. This in turn actuates limit switch 57 mounted on theloader lift arm assembly when it touches the truck body. Limit switch 57and 45 are normally mechanically retracted out of harms way to preventmechanical damage when the lift arms are lowered and are only extendedin operating position when the lift arms are raised in position to dump.As soon as limit switch 57 is actuated, the circuit is completed tosolenoid automatic dump valve 21 and hydraulic fluid under pressure issupplied through valve 21 to the bucket dump ram 5 which tilts it to thedump position. When the bucket is in full dump position, limit switch 55mounted on the lift arm assembly is actuated by the bucket and opens thecircuit to the solenoid dump valve 21, which in turn blocks the bucketram 5 in the dump position.

As in the automatic loading cycle, the automatic dump cycle'can bestopped at any time either by opening the master control switch 10, themode selector switch auto dump 12, or by operating either of the manualcontrol valves 8A and 8B which in turn will open their respective limitswitches 37 and 39. Any of the preceding operations will deenergize theautomatic raise valve 21. However, as soon as the manual control valvesare returned to the neutral position, their limit switches will closeand restart the dump cycle where it stopped.

For the automatic lower cycle, positioned in parallel with the manualvalves 8A and 88, respectively, are solenoid operated two-positionvalves, lift arm automatic lower valve 22 and bucket automatic lower-.valve.23. The lift arm automatic lower valve 22 controls hydraulicfluid pressure to the lower side of ram 4 when the solenoid 22a isenergized, and blocks the movement of the rams 4 when the solenoid isdeenergized. The bucket automatic lower valve 23 controls hydraulicfluid pressure to the curl side of the bucket rams 5 when the solenoid23a is energized and blocks the movement of the bucket 3 when thesolenoid 23a is deenergized. The operation of the automatic lower cycleis initiated when the operator energizes the master automatic switch 10and mode selector switch auto lower 13. At this time the lift arms arein the raised position closing limit switch 41 mounted on the carrier 1,the bucket 3 is in the dump position closing limit switch 47 mounted onthe lift arm assembly. Also at this time the operator shifts the carrierinto reverse closing limit switch 49 mounted on the gear shift. Thecarrier backs away from the truck closing limit switch 45 mounted on thelift arms which had previously been in contact with the truck body. Assoon as limit switch 45 closes, a circuit is completed to the auxiliaryrelay 43, the contacts on the 43 relay close and hole the relayenergized regardless of whether or not the transmission is now placed inreverse or forward gear. At the same time that the auxiliary relay 43 isenergized, a circuit is completed through the solenoid 23a of the bucketautomatic lower valve 23.

Hydraulic fluid under pressure is supplied via hydraulic line 50 at fullvolume through valve 23 to the bucket curl ram 5. This causes the bucket3 to tilt from the dump position to'the load position. When the bucketis in the proper position for loading, limit switch 51 mounted on thelift arm assembly is actuated by the bucket 3. This opens the circuit tothe solenoid 23a of valve 23, which in turn blocks the bucket ram 5 inthe load position. At the same time that the automatic bucket lowervalve is energized, delay timer 24 to the automatic lift arm lower valve23 is energized. The amount of delay is preset by the operator to allowsufficient time for the loader bucket to finish clearing the sides ofthe truck before the lift arms start to lower. At the end of the presetinterval, a contact in delay timer 24 is closed and the automatic liftarm lower valve 22 is energized. Hydraulic fluid under pressure nowflows through valve 22 to the lift arm cylinder 4, lowering the bucketdown toward the ground. When the bucket 3 reaches the proper heightabove the ground for loading, a preset limit switch 41 mounted on thecarrier 1 contacts the lift arm 2. The limit switch contact 41 thenopens deenergizing both the auxiliary relay 43 and the automatic liftarm lower valve 22. This in turn shuts off the fluid flow from the liftarm rams 4 and holds the bucket 3 at the correct height for loading.Relay 43 cannot be reenergized as limit switch 47 mounted on the liftarm assembly is opened by the bucket as soon as it moves out of the dumpposition toward the load position.

As in the automatic loading cycle, the automatic lower cycle can bestopped at any time either by opening the master control switch 10, themode selector switch auto lower 13, or by operating either of the manualcontrol valves 8A and 8B which in turn will open their respective limitswitches 37 and 39. Any of the preceding operations will deenergize theauxiliary relay 43, the automatic lift arm lower valve 22 and theautomatic bucket lower valve 23. However, as soon as the manual controlvalves are returned to'the neutral position, their limit switches willclose and restart the automatic lower cycle where it stopped providedthat the transmission is still in reverse and the bucket has not movedfar enough out of the dump position to trip limit switch 47 mentionedpreviously.

The loader has now completed its cycle and is ready to start theautomatic loading cycle again whenever the operator drives the bucket 3into the spoil pile. From the previous description it is seen that anyof the cycles can be performed either automatically or manually withoutaffecting the operation of the following cycle. The portions can bepreselected by the mode selector switches 9, 11, 12, 13 by eithersetting them in the automatic or manual position at the operatorsdiscretion.

in the working embodiment of the systems of this invention, it isdesirable that flow control valves be utilized in certain instances toslow the action of the hydraulic cylinders. in addition, devices tocushion the stopping of the cylinders may be desired plus pressurerelief valves, filters, etc. Since such devices are well known in theindustry and are not basic to the systems of this invention, they havenot been shown. Also, the system has been described in its simplest formfor easy comprehension of the various elements involved. In actualpractice, economy would probably be achieved by combining some of thevalves as shown in FIG. 3. In this embodiment valves 21 and 23 arecombined into one valve with dual solenoids, 21a and 23a. When solenoid21a is energized the bucket moves in the dump direction and whensolenoid 23a is energized the bucket moves in the curl position. Inaddition, valve 17 is eliminated and the control circuit for solenoid17a is connected to solenoid 230 through an isolating diode 31. Valves16 and 22 are combined into one valve with dual solenoids 16a and 22a.When solenoid 16a is energized, the lift arms move in the raise positionand if solenoid 22a is energized, the lift arms move in the lowerposition.

Referring now to FIG. 4, a pictorial flow diagram is shown of the basichydraulic circuit of this invention, wherein the loading, raising,carrying, dumping, and repositioning for loading cycles areautomatically controlled. Since FIG. 4 differs from FIG. 3 in thecontrol of the loading cycle only, this is the only portion that will bedescribed. In this embodiment the control transducer is located onbucket arms to measure the loading reference.

With specific reference to FIG. 4 and general reference to FIGS. 1, 2and 3 for the automatic loading cycle, there is positioned in parallelwith the manual valves 8A and 8B the solenoid operated two positionautomatic load valve 7. The function of the valve is to control thehydraulic fluid pressure to the lift side of the lift ram 4 and the curlside of the bucket ram 5 (FIG. I). When not energized, the solenoid 7ablocks the movement of the rams. The operation of the hydraulic circuitis initiated when the lift arms are lowered to the digging positionclosing limit switch 26 mounted on the carrier 1, and the bucket isleveled to the loading attitude closing limit switch 27 mounted on thelift arm assembly. This causes the mode selector switch 9 and the masterautomatic switch 10 (both shown in FIG. 2) to become energized. Thetransmission of the carrier at this time is in low gear closing limitswitch 28 as the operator drives the loader bucket into the spoil pile.When the bucket encounters sufficient resistance, the load on thetransducer 52 will rise and transmit a signal to the switch 61.

The transducer 52 could be placed in several different places to measurethe loading force on the bucket or forks, such as on the lift arm 2connection 2A to the loader 7 to measure the horizontal loading force,on the lift arm 2 to bucket 3 connection 28 to measure the horizontalloading force on the bucket, in the lift arm 2 itself to measure theforce along the lift arms, or in the driving train from the carrierengine to the carrier wheels or tracks. If the carrier were of the typeto be electrically propelled, the transducer 52 could be placed tomeasure the current flow to the propelling motors. If the carrier 1 waspropelled by hydraulic motors, the transducer 52 could be placed tomeasure the pressure to the hydraulic motors, etc.

The signal level at which the contacts of 61 close is adjustable duringthe cycle by the operator depending upon the type of soil being loadedand the condition of the ground the loader is operating on.

At a preset signal from the transducer 52, somewhere just below thestall point of the carrier, contacts 6l will close and energize thesolenoid 7a of the automatic loading valve 7. Fluid will flow from thecarrier source to the flow divider (FIG. 2) and then to the lift side ofthe lift ram 4 and the curl side of the bucket ram 5 (FIG. 1). The flowdivider 15 will insure that the bucket 3 will curl in a predeterminedratio to the amount of lift of the bucket. As the bucket lifts and curlsin the spoil pile, the resistance to the carrier bucket 3 will decreaseand the loader will drive bucket 3 deeper into the spoil pile. At thesame time, the lessened resistance to the bucket will decrease thesignal level from the transducer 52, open the contacts of switch 61 andstop the movement of the bucket until sufficient bucket resistance isagain encountered to start the cycle all over again. In this fashion,the carrier will continually move into the spoil pile under the constantdrive from the its engine and the bucket will raise and curl to obtain afull load.

As soon as the bucket is full, the operator reverses the carrier. thisopens limit switch 28 and deenergizes the automatic loading solenoidvalve 7. At any time the automatic loading cycle can be stopped byeither opening the master control switch 10, the mode selector switchauto load 9, or by operat ing either of the manual control valves 8A and8B which in turn will open their respective limit switches 37 and 39(FIG. 2). Any of the above operations will deenergize the automaticloading solenoid valve 7. However, as soon as the manual control valves8 are returned to the neutral position, their limit switches 37 and 39will close and restart the loading cycle in a position where it wasinterrupted.

Referring now to FIG. 5, a pictorial flow diagram is shown of the basichydraulic circuit of the present invention, wherein the loading,raising, carrying, dumping and repositioning for the digging cycles areautomatically controlled. Since FIG. 5 differs from FIG. 3 in thecontrol of the loading cycle only. this is the only portion of FIG. 5that will be described.

With specific reference to FIG. 5 and with general reference to FIGS. 1,2, and 3 for the automatic loading cycle, there is positioned inparallel with the manual valves 8A and 8B the power operated twoposition automatic load modulating valve 54. The valve 54 controlshydraulic fluid pressure to the lift side of the lift ram 4 (FIG. 3) andthe curl side of the bucket ram 5 (FIG. 3) when the modulating valve 54is energized and blocks the movement of the rams when the valve 54 isdeenergized. The operation of the hydraulic circuit is initiated whenthe lift arms 2 are lowered to the loading position, closing limitswitch 26 mounted on the carrier 1. At this time the bucket is leveledto the loading attitude closing limit switch 27 mounted on the lift armassembly. This causes the mode selector switch auto load 9 and themaster automatic switch 10 (FIG. 3) to become energized. Thetransmission of the carrier at this time is in low gear closing limitswitch 28 which in turn will energize the two position solenoid valve56. This last named valve 56 controls the flow of the torque converterpressure to the modulating operator of the automatic load valve 54.

In operation, as the operator drives the bucket 3 into the spoil pilethe bucket 3 will encounter resistance. When sufficient resistance ismet, the pressure in the torque converter 14 will rise and in turn therising pressure will be transmitted to the modulating actuator of theautomatic load valve 54.

The amount of pressure required to start modulating valve 54 isadjustable during the cycle by the operator depending upon the type ofsoil being loaded and the condition of the ground the loader isoperating on. Generally, the modulating valve 54 will be preset by theoperator to a value that it raises and curls the bucket 3 just beforethe carrier stalls or starts to spin its wheels, whichever occurs first.

At the preset pressure from the torque converter, valve 54 will start toopen and fluid will flow from the carrier source to the flow dividerlS(FIG. 3) and then to the lift side of the lift ram 4 (FIG. 3) and thecurl side of the bucket ram 5 (FIG. 3). The flow divider 15 will insurethat the bucket will curl in a predetermined ratio to the amount of liftof the bucket. As the bucket lifts and curls in the spoil pile, theresistance to the loader bucket will decrease and the loader will drivedeeper into the spoil pile. At the same time, the lessened resistance tothe bucket will decrease the pressure in the torque converter 14, andstart to close valve 54 which will slow the rate of lifting and curlingof the bucket. If the resistance to the loader bucket is lessenedsufficiently to drop the pressure from the torque converter 14 below thepreset value required to operate valve 54, valve 54 will closecompletely and the lifting and curling of the bucket will be stoppeduntil sufficient resistance is again encountered to start the cycle allover again. Accordingly, the carrier continually moves toward the spoilpile under the constant drive of the engine and the bucket 3 raises andcurls in direct proportion to the horizontal bucket loading resistanceto obtain a full load. As soon as the bucket is full, the operatorreverses the carrier, this opens limit switch 28 and deenergizessolenoid valve 56 which in turn shuts off the modulating signal flow tothe automatic load valve 54 and shuts down the automatic loading cycle.

At any time the automatic loading cycle can be stopped by either openingthe master control switch 10 (FIG. 3) the mode selector switch auto load9, or by operating either of the manual control valves 8A and 8B whichin turn will open their respective limit switches 37 and 39 (FIG. 3).Any of the above operations will deenergize the control solenoid valve56 which in turn will close the automatic load valve 54. However, assoon as the manual control valves are returned to their neutralposition, their limit switches 37 and 39 (FIG. 3) will close and restartthe loading cycle where it was interrupted.

Referring now to FIG. 6, a pictorial flow diagram is shown of the basichydraulic circuit of the present invention, wherein the loading,raising, carrying, dumping and repositioning for the digging cycles areautomatically controlled. Since FIG. 6 differs from FIG. 3 in thecontrol of the loading cycle only, this is the only portion of FIG. 6that will be described.

With specific reference to FIG. 6 and general reference to FIGS. 1, 2and 3, for the automatic loading cycle, there is positioned in parallelwith the manual valves 8A and 88 (FIG. 3) the power operatedtwo-position automatic load modulating valve 54. This valve controlshydraulic fluid pressure to the lift side of the lift ram 4 (FIG. 3) andthe curl side of the bucket ram 5 (FIG. 3) when the modulating valve 54is energized and blocks the movement of the rams when the valve 54 isdeenergized. The operation of the hydraulic circuit is initiated whenthe lift arms 2 are lowered to the loading position, closing limitswitch 26 mounted on the carrier 1. At this time the bucket 3 is leveledto the loading attitude, closing limit switch 27 mounted on the lift armassembly 2. This causes the mode selector switch auto load 9 and themaster automatic switch 10 (FIG. 3) to become energized. Thetransmission of the carrier is in low gear closing limit switch 28 whichin turn will energize the two position solenoid valve 56. This valvecontrols the signal flow from transducer 52 to the modulating operatorof the automatic load valve 54.

In operation, as the operator drives the bucket 3 into the spoil pile,the bucket will encounter resistance, when sufficient resistance is met,the load on the transducer 52 will rise and in turn transmit a signalthrough the solenoid valve 52 to the modulating actuator of theautomatic load valve 54.

The transducer 52 could be placed in several different positions tomeasure the loading force on the bucket 3 or forks, such as on the liftarm 2 connection 2A to the carrier 1 to measure the horizontal loadingforce, on the lift arm 2 to bucket 3 connection 28 to measure thehorizontal loading force on the bucket, in the lift arm 2 itself tomeasure the force along the lift arms, in the driving train from theloader engine to the loader wheels or tracks, if the loader waselectrically propelled, the transducer 52 could be placed to measure thecurrent flow to the propelling motors, if the loader was propelled byhydraulic motors, the transducer 52 could be placed to measure thepressure to the hydraulic motors, etc.

The signal level required to start modulating valve 54 is adjustableduring the load cycle by the operator depending upon the type of soilbeing loaded and the condition of the ground the loader is operating on.Generally, the modulating valve 54 will be preset by the operator to avalue that it raises and curls the bucket just before the carrier stallsor starts to spin its wheels, whichever occurs first.

At a preset signal level from the transducer 52, valve 54 will start toopen and fluid will flow from the carrier source to the flow divider(FIG. 3) and then to the lift side of the lift ram 4 (FIG. 3) and thecurl side ofthe bucket ram 5 (FIG. 3). The flow divider will insure thatthe bucket will curl in a predetermined ratio to the amount of lift ofthe bucket. As the bucket 3 lifts and curls in the pile, the resistanceto the loader bucket 3 will decrease and the carrier 1 will drive deeperinto the spoil pile. At the same time, the lessened resistance to thebucket 3 will decrease the pressure on the transducer 52 and start toclose valve 54, which will slow down the rate of lifting and curling ofthe bucket 3. If the resistance to the loader bucket 3 is lessenedsufficiently to drop the signal level from the transducer 52 below thepreset value required to operate valve 54, valve 54 will closecompletely and the lifting and curling of the bucket 3 will be stoppeduntil sufficient resistance is again encountered to start the cycle allover again. Accordingly, the carrier 1 continually moves into the spoilpile under the constant drive of the engine and the bucket 3 raises andcurls in direct proportion to the horizontal bucket loading resistanceto obtain a full load in an efficient manner. As soon as the bucket 3 isfull, the operator reverses the carrier, this opens limit switch 28 anddeenergizes solenoid valve 56 which in turn shuts off the modulatingsignal flow to the automatic load valve 54 and shuts down the automaticloading cycle.

At any time the automatic loading cycle can be stopped by either openingthe master control switch 10 (FIG. 3). the mode selector switch autoload 9 or by operating either of the manual control valves 8A and 8B(FIG. 3) which in turn will open their respective limit switches 37 and39 (FIG. 3). Any of the above operations will deenergize the controlsolenoid valve 56 which in turn will shut down the automatic load valve54. However, as soon as the manual control valves 8 (FIG. 3) arereturned to their neutral position, their limit switches 37 and 39 (FIG.3) will close and restart the loading cycle where it was interrupted.

Although certain and specific embodiments have been shown it is to beunderstood that modifications may be made without departing from thetrue spirit and scope of the invention.

What is claimed is:

1. An automatic control system for a front end loader of the typewherein a lift arm carrying a tiltable bucket is mounted on aself-propelled carrier which drives the lift arm and bucket into thematerial to be loaded, the improvement comprising: automatic controlmeans for actuating said lift arm; automatic control means for actuatingthe tilt of said bucket; pressure sensing means associated with thehorizontal loading resistance encountered by said bucket upon engagementwith the material being loaded; transducer means connected to saidpressure sensing means to provide a signal output related to the loadingresistance sensed; switch means operatively connected to said transducermeans and to each of said automatic control means to selectively actuatesaid control means responsive to a predetermined pressure value; manualcontrol means for overriding each of said automatic control means; andsecond switching means responsive to a second sensed pressure signalindicating a given vertical load on said bucket, said second switchingmeans activating said automatic control means to fully tilt said bucketto a carry position.

2. The automatic control system of claim 1 further including thirdswitch means actuated when said bucket moves to a fully tilted carryposition to activate the raising of said lift arm to a predeterminedcarry position.

3. The automatic control system of claim 1 including means for adjustingthe rate which said lift arm raise to said carry position.

4. The automatic control system of claim 1 including switch meansactivated upon contact to actuate tilting said bucket from a carryposition to a dump position and further including means responsive toreversing said carrier to automatically actuate the tilting of saidbucket from said dumping position to a loading position and to actuatesaid lift arms to lower at a predetermined rate to a predeterminedloading position.

1. An automatic control system for a front end loader of the typewherein a lift arm carrying a tiltable bucket is mounted on aself-propelled carrier which drives the lift arm and bucket into thematerial to be loaded, the improvement comprising: automatic controlmeans for actuating said lift arm; automatic control means for actuatingthe tilt of said bucket; pressure sensing means associated with thehorizontal loading resistance encountered by said bucket upon engagementwith the material being loaded; transducer means connected to saidpressure sensing means to provide a signal output related to the loadingresistance sensed; switch means operatively connected to said transducermeans and to each of said automatic control means to selectively actuatesaid control means responsive to a predetermined pressure value; manualcontrol means for overriding each of said automatic control means; andsecond switching means responsive to a second sensed pressure signalindicating a given vertical load on said bucket, said second switchingmeans activating said automatic control means to fully tilt said bucketto a carry position.
 2. The automatic control system of claim 1 furtherincluding third switch means actuated when said bucket moves to a fullytilted carry position to activate the raising of said lift arm to apredetermined carry position.
 3. The automatic control system of claim 1including means for adjusting the rate which said lift arm raise to saidcarry position.
 4. The automatic control system of claim 1 includingswitch means activated upon contact to actuate tilting said bucket froma carry position to a dump position and further including meansresponsive to reversing said carrier to automatically actuate thetilting of said bucket from said dumping position to a loading positionand to actuate said lift arms to lower at a predetermined rate to apredetermined loading position.